GNSS buoy array in the ocean for natural hazard mitigation. Teruyuki KATO Earthquake Research Institute the University of Tokyo, Japan

Transcription

1 GNSS buoy array in the ocean for natural hazard mitigation Teruyuki KATO Earthquake Research Institute the University of Tokyo, Japan 1

2 GNSS applications in Earth science From static to high-rate observations Applications by static observations (30 sec) Crustal deformations, plate motions Earthquake mechanisms, volcanic eruptions, Discovery of slow slip events along subduction zones GPS meteorology, Ionospheric monitoring Applications by high-rate observations (1 Hz) GPS seismometer GPS-acoustic system for ocean bottom crustal movements monitoring GPS buoy for, first, tsunami monitoring, then, application to meteorology and ionosphere in the ocean 2

3 Basic concept GPS Satellite Base Station GPS Tsunami Meter Data 3

4 Contents Review of developments of GPS buoy Lessons from the 11 March 2011 Tohoku-oki tsunami Recent developments for solving the problems Further developments for applying to the ocean bottom crustal deformation monitoring, meteorology and ionospheric monitoring Summary and outlook 4

5 Proto-type GPS buoy first experiment - January

6 GPS buoy for operational test off Ofunato, northeastern Japan Tokachi Data were transmitted to the City Hall and Fire station 1.6km φ:2.8m H:8.2m Weight:12ton Water depth:50m 6

7 Peru Earthquake JST25/06/2001 Original 1Hz data 7

8 Peru Earthquake JST25/06/2001 Filtered buoy data and tide gauge data Tsunami GPS Buoy Tide Gauge 25 June 2001 (JST) 8

9 GPS buoys implemented as wave meter operated as a national wave monitor system NOWPHAS (From ERI HP) System uses RTK GPS and data transmission by radio. Placed within 20km from the coast. Established at 15 sites as of Real time monitor on the Web is available. 9

10 Observed tsunamis due to the Tohoku-Oki earthquake on 11th March 2011 by GPS buoys Off North Iwate (Kuji) Off Central Iwate (miyako) Off South Iwate (Kamaishi) EQ 10 (Courtesy of Port and Airport Research Institute)

11 Lessons from the 11 March Tohoku-oki tsunami and their countermeasures GPS buoy should be placed much farther offshore for effective early warning (>100km) Problems to be solved for far-offshore buoy deployments 1. Baseline mode kinematic observation has distance limit for accurate measurements (<20km). New algorithm of Precise Point Positioning should be introduced 2. Surface radio system is not adequate for long distance data transmission Data transmission via satellite is needed 11

12 New algorithm: PPP-AR (Precise Point Positioning with Ambiguity Resolution) GPS satellite IGS (International GNSS Service) Precise orbit (sat. orbit and clock) + correction by GEONET) GPS receiver Control station 1Hz data GEONET Conventional PPP uses only IGS orbits/clock. New PPP-AR uses corrections by GEONET data 12 T15,O48

13 Experiments with QZSS & ETS VIII (Michibiki) (Kiku 8) Period of experiments 16 Dec Jan., Jun., 2014 Purpose - Correction data transmission using LEX/QZSS - Positioning data transmission via ETS-VIII. - Real-time data dissemination through internet 13

14 Experiments with QZSS & ETS VIII 14

15 Experiments with QZSS & ETS VIII 15

16 Experiment with QZSS & ETS VIII Transmission rates Significant wave height Transmission rates Significant wave height Lapse time since 9AM, 18 June

17 Experiment with QZSS & ETS VIII Temporal change of elevation angle Antenna gain w.r.t. zenith angle Plane antenna 17

18 Multi purpose GNSS buoy for disaster mitigation Tsunami early warning as well as wave monitoring is already operation Ocean bottom crustal movements Continuous monitoring by GPS/Acoustic system Atmospheric research (GPS meteorology) Contribution to weather forecast Ionospheric research Contribution to space weather forecast Ocean surface monitoring with ancillary equips High speed satellite communication is required 18

19 Ocean bottom crustal movement observation using GPS/Acoustic system 0.40 GPS satellites West <-> East (m) /- 0.2 cm/year RMS=0.6cm GPS base station Acoustic ranging Kinematic GPS Survey vessel South <-> North (m) /- 0.4 cm/year RMS=1.2cm Ocean bottom stations Slides provided by Mariko Sato (Japan Coast Guard) 19

20 Application to ocean bottom crustal movements monitoring using GNSS buoy GNSS sat. Receiving sonic wave GPS buoy Sending sonic wave radio trans. Radio relay station Internet Kochi N. C. Ocean bottom station (3 sets) 20

21 Experiment in 2013 Deployments of ocean bottom stations 29 July 2013 CTD observation: 31 July 2013 GPS/Acoustic ranging using buoy: 2 August 2 October, 2013 GPS/acoustic ranging using a boat: 31 July

22 Comparison of received acoustic waves Acoustic waves using a boat Acoustic waves using a buoy Correlation coefficient: 0.2 Correlation coefficient:

23 Application of GNSS buoy for weather forecast GPS buoy and GEONET sites Time series of ZTD between GEONET(1121) and buoy Comparison is made between buoy and the GEONET site of the lowest height nearby the buoy. Data period: 1-16 August 2008 Time series at the buoy ( ) is generally consistent with that on the ground ( ), yet the former differs from the latter at some time periods. More satellite number provides better agreement between the two, implying adding satellites other than GPS, such as GLONASS, may improve the results. 10 satellites 6 satellites 23 (Y. Shoji:Spring Meeting of MSJ 2010)

24 TEC variation observed at the 2011 Tohoku earthquake by NICT TEC variation observed using GEONET data. Short period variations with less than 10 minutes of periods are shown. X indicates ionospheric epicenter. Concentric circle is centered at the ionospheric epicenter. Cut-off elevation angle is 15deg. 24 (translated from the slide by Tsugawa)

25 Global ground-based GNSS network - Next step to the oceanic region - More than 5,000 ground-based GNSS sites data are available online as of Jan. 2012, over the world. More distributed GNSS sites in the ocean, together with more GNSS satellites, improves spatial resolution and decreases blank area. 25 (translated from the slide by Tsugawa)

26 Proposal of GNSS buoy array in the western Pacific Expected cost for 81 sites: (Very coarse!) Construction 300million$ Operation 10million$/yr Feasible? or Not? (81 sites in the Japanese EEZ; Modified from Tsugawa et al., 2012) 26

27 Summary Current GNSS buoy system uses baseline mode and has limits of distance up to 20km. We are testing a system that would be deployed at far offshore of 100km or more. A new algorithm of PPP-AR is successfully applied to the system. Test of satellite data transmission has been successful. If it is capable of deploying GNSS buoy at far offshore, a GNSS buoy array in the western Pacific or elsewhere would be a next challenge for multi-purpose disaster mitigation infrastructure in the region. 27

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